Recently, terrestrial digital broadcasting has started. Following the start of the terrestrial digital broadcasting, various digital broadcasting receiver apparatuses and digital broadcasting reception methods have been proposed (See, for example, Japanese patent laid-open publication Nos. 2002-300128, 2002-218341, 2002-135808 and 2001-197025, and Japanese Patent No. 3,389,843).
In the digital broadcasting receiver apparatus, a digital broadcasting reception functional module is expensive. Due to this, such an apparatus to which the digital broadcasting reception functional module can be attached as an optional unit, and a main body of which is inexpensive, is often more attractive to a user than such an expensive apparatus that contains the digital broadcasting reception functional module. The present invention realizes a functional module card that includes a digital broadcasting reception function and an inexpensive host apparatus to which the functional module card can be attached as an optional unit.
Upon realizing such a functional module card and such a host apparatus, the following two problems arise.
(i) First Problem
It is attractive to a user that the digital broadcasting reception function can be installed into a functional module card that includes a highly versatile interface, because range of user's selection of a host apparatus and an option is widened. If the functional module card that includes the highly versatile interface includes not only the digital broadcasting reception function but also the other functions, the functional module card is further attractive to the user. Conversely, if a functional module card that includes the digital broadcasting reception function can be connected to a host apparatus only via an exclusive interface, the functional module card can be attached only to a specific host apparatus, and only a specific functional module card can be attached to a host apparatus. This results in quite restrictive variations in a combination of a host apparatus and a functional module card. Such a functional module card tends to be expensive. In addition, restricted range of user's selection of a host apparatus and an option makes these products less attractive to the user.
However, generally speaking, a versatile functional module card communicates with a host apparatus by use of a master-slave communication (in which the host apparatus generates a communication clock) in which the host apparatus operates as a master apparatus and the functional module card operates as a slave apparatus. On the other hand, it is basically necessary to process and output such a digital broadcasting signal that is continuous relative to a time axis in response to such a clock that is generated from the digital broadcasting signal. Otherwise, no signal time (image (or sound) blackout or freeze) or such a state that a signal cannot be outputted and should be abandoned (image or sound skipping) may possibly occur. A method for controlling a communication clock for the versatile functional module card completely differs from a method for controlling the clock generated from the digital broadcasting signal. Accordingly, even if the digital broadcasting signal reception function is installed into a functional module card according to a prior art that includes the versatile interface, the first problem arises that the digital broadcasting signal cannot be transferred to the host apparatus in response to a correct clock.
It is an object of the present invention to provide a functional module card that includes the versatile interface and the digital broadcasting signal reception function, and transfers the digital broadcasting signal to a host apparatus in response to the correct clock, a host apparatus corresponding to the functional module card, a method for controlling the functional module card, and a method for controlling the host apparatus.
(ii) Second Problem
In the pay digital broadcasting, a broadcasting station transmits a scrambled or an encrypted digital broadcasting signal and loads such information that is necessary to descramble or decode the digital broadcasting signal to an apparatus owned by a user who pays charges. With doing so, only the user who has paid the charges can view a digital broadcasting content. However, if the functional module card includes the digital broadcasting reception function, a plurality of users can illegally view the digital broadcasting content by sharing one functional module card among the users and allowing one user to pay charges for the digital broadcasting content to the broadcasting station. Namely, a second problem arises that copyrights of digital contents transmitted from the broadcasting station cannot be protected.
It is an object of the present invention to provide a functional module card that includes a digital broadcasting reception function, that can be attached to a host apparatus as an optional unit, and that can protect copyrights of broadcast digital contents, an inexpensive host apparatus corresponding to the functional module card, a method for controlling the functional module card, and a method for controlling the host apparatus.